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METHYL ALCOHOL

39

(c) PERMANGANATE TEST. 5 c.c. of the alcohol are treated with i c.c.
of 0-1% permanganate solution. With pure methyl alcohol the pink colora-
tion persists, whereas with the commercial product, either crude or rectified,
the permanganate is instantly decolorised.

A.    Pure Methyl Alcohol

The tests to be made are as follows :

1.  Sulphuric Acid Test (vide supra).

2.  Permanganate Test (vide supra).

3.  Non-volatile Substances.—50 c.c. evaporated on a  steam-bath
should leave no appreciable residue.

4.  Acidity or Alkalinity.—15-20 c.c. of the alcohol are mixed with
an equal volume of water coloured with neutral litmus, the colour of which
should not be altered in the mixture.

5.  Solubility in Water.—15-20 c.c. of the alcohol, mixed with water
in any proportion, should give a clear solution.

6.  Solubility in Caustic Soda Solution.—15-20 c.c. of the alcohol,
mixed with concentrated sodium hydroxide solution, should yield a colour-
less solution (absence of aldehydes).

7.  Distillation.'—50 c.c.  of the alcohol, when distilled, should pass
over within 0-5° (a 100 c.c. copper flask with side-tube is best).

8.  Acetone.—i c.c. of the alcohol is treated with 10 c.c. of 10% sodium
hydroxide solution and 5 drops of  approximately N/io-solution of iodine
in potassium iodide.    Even after some time no turbidity, due to iodoform,
should be formed (for quantitative determination, see later).

9.  Determination of the Methyl Alcohol.—The content of methyl
alcohol is deduced from the specific gravity by means of Klason and Norton's
tables (seepage 40).

B.    Commercial Methyl Alcohol, Crude or Rectified

The tests commonly made are :

1.  Acidity or Alkalinity.—The alcohol is tested with very sensitive
litmus paper or, if the product is colourless, with neutral litmus tincture
or methyl orange.

2.  Alcoholometric Degree.—In practice use is made of Gay-Lussac's
alcoholometer at 15° or that of Tralles at 15-56°.   Although these alcoholo-
meters are graduated for ethyl alcohol, they are used for methyl alcohol,
aqueous mixtures of the latter having densities approximating to those
of water-ethyl alcohol mixtures.

3.  Distillation.—This is carried out on 100 c.c., using the flask described
for the distillation of pyridine bases (see chapter on Tar and its Products),
the fractions distilling over for each 5° being collected separately in graduated
cylinders.

4.  Solubility in Water.—<io c.c. are mixed in a 100 c.c. cylinder with
10 c.c. of water and any turbidity noted ;  30 c.c. of water are then added,
and later further quantities to 100 c.c., any formation of opalescence being
observed.commercial alcohol,, whether